In the field of gas production, a need exists for means for producing tritium from lithium with neutrons having energies of 2.45 MeV, 14.1 MeV and 14.7 MeV. However, the methods and apparatus proposed heretofore that have employed liquid lithium as the breeding medium, as described in Princeton Plasma Physics Laboratory Report MATT-1050, have involved difficult problems of material compatibility, corrosion, or the movement of liquid metals in magnetic fields. It has also been advantageous to provide tritium producing apparatus and methods having reliability and long operating times.